Pyrotechnically controlled mechanical stepping drive

ABSTRACT

The present invention concerns a pyrotechnically controlled stepping drive that may be used for missiles, torpedoes and for any driving action where some danger is present. The device comprises a motor-drawer moving in a guide which supports igniters. A piston slides within this drawer and allows expansion of the gases generated by igniter triggering. A double lock system with one lock per side opposite the motion can be used to increase reliability and make the system insensitive to vibrations.

United States Patent Hamon 1 May 27, 1975 1 PYROTECHNICALLY CONTROLLED [56} References Cited MECHANICAL STEPPING DRIVE UNITED STATES PATENTS [75] Inventor: Emile F. J. Ham n, 2,096,619 10 1937 Prince 60/2611 La-Seyne-sur-Mer, France 2,805,066 9/1957 Mongello 60/261 1 [73] Assignee: Etat Francais, Delegation Ministerieue pm" liArmemem Primary Examiner-Robert F. Stahl Paris France Attorney, Agent, or FirmStevens, Davis, Miller &

. Mosher [22] Filed: Oct. 24, 1972 [2]] Appl. No.: 261,108 [57] ABSTRACT [30] Foreign Application Priority Data Mar. 3, 1972 France 72.07354 Mar. 3, 1972 France 72.07355 [52] US. Cl 89/1 B; 60/534; 102/376; 102/70 [51] Int. Cl. F02n 13/00 [58] Field of Search 74/112; 60/261, 2611, 60/634; 89/1 R, 1 B, 1 D, 1 K; 102/495, 27, 1, 37.6

The present invention concerns a pyrotechnically controlled stepping drive that may be used for missiles, torpedoes and for any driving action where some danger is present. The device comprises a motor-drawer moving in a guide which supports igniters. A piston slides within this drawer and allows expansion of the gases generated by igniter triggering. A double lock system with one lock per side opposite the motion can be used to increase reliability and make the system insensitive to vibrations.

13 Claims, 21 Drawing Figures EflaTEPfTEDFLlYE? ms 3885.451

SHEET 1 FIG.1. FIG'Z ACTUATOR ELECTRONICS TTTHT EVENTS PYROTECIINICALLY CONTROLLED MECHANICAL STEPPING DRIVE This invention concerns a pyrotechnically controlled. mechanical stepping device allowing rectilinear or circular displacement.

Activation of a load circuit (ignition, pyrotechnic alignment, valve control) is diagrammatically shown in FIG. 1 and is generally achieved by starting actuators such as relays and motors which are controlled by elec tronic circuitry which is itself subject to a sequence of events.

Safety and reliability require a large number of events acquiescing to the functioning of the device and therefore demand control electronics of an elaborate nature that may not be exposed to too severe an environment (vibration, impacts, thermal or electromagnetic radiations].

A random signal at the threshold value of one of these actuators or at that of its control organs may trigger functioning independently of the other conditions or circumstances as far as present systems are con cerned.

The present invention concerns a device which is insensitive to vibrations, impacts, thermal or electromagnetic radiations and which makes such random triggers impossible while at the same time introducing considerable simplification pertaining to the system as a whole as illustrated diagrammatically in FIG. 2.

The events are fed directly to the mechanical device so that each time rotation occurs from A to B by one discrete step, the desired action is permitted to happen.

Rotation from A towards B (in the diagram of FIG. 2) may only occur mechanically when a control sequence unfolds exactly as programmed; any unforeseen command occurring at a time other than opportune or in the proper sequence may irreversibly freeze the sys tern.

Furthermore total safety is insured at every step by means of a mechanical bolting scheme inherent to the invention and therefore preventing sudden motions from A to B.

According to the invention, the pyrotechnically controlled, mechanical stepping drive with either translational or rotational motion comprises, in one principal embodiment, a motor-drawer moving within a guide provided with igniters and mechanically locked at the end of each motion and prepared at that time for the next ignition. The drawer-system comprises a stop which in the stationary position of the device is located in an orifice leading to the igniter and which upon ignition is pulled out of the way so that motion may occur. Also, this drawer-system comprises a piston sliding in the inside of the drawer and locking into place by means of a pawl or a stop while sealing the gases escape hole when the drawer has run its course, thus making the next ignition sequence possible. The pistons motion is caused either by a return spring or by an auxiliary igniter, the ignition of which is synchro nized with the principal ignition. The guide provided with igniters also is provided with gas escape holes and with socket-like openings for accepting the pawl or the stop of the piston and they are so arrayed that the piston will seal the gas escape holes when it is in the locked position.

In a second principal embodiment, a plurality of modular units are connected end-to-end to form an elongated cylindrical guide path in which a piston travels in a forward direction. Each module has a shutter at its front end which locks the piston in a given module until the ignitor in that module is fired. The expanding gases releases the shutter from its locking engagement with the piston allowing the latter to move forward into the next succeeding module and the former to drop down to seal the cylinder behind the piston to create a baffle against which the expanding gases operate to push the piston forward.

In a third principal embodiment, the linear motion of a piston contained in a rotor element is translated into rotational motion of the rotor and a shaft to which the rotor is connected.

The invention will be more fully described below by means of the specific embodiments shown in the attached drawings, in which:

FIGS. 1 and 2 are block diagrams conceptually representing prior art systems and the present invention, respectively;

FIG. 3 shows a front sectional view of one embodiment of the present invention, having translational motion and a single locking arrangement, taken along the line III-III in FIG. 4;

FIG. 4 shows a side sectional view of the first embodiment along the line IVIV in FIG. 5;

FIG. 5 shows a top sectional view taken along the line VV in FIG. 4',

FIG. 6 shows a side sectional view of a second embodiment of the present invention, having rotational motion and a single locking arrangement, taken along the line VI-VI in FIG. 7',

FIG. 7 shows a part sectional top view of the embodiment of FIG. 6 taken along the line VIIVII;

FIG. 8 shows a front sectional view of a third embodiment, having translational motion and a double locking arrangement, taken along the line VIIIVI[I in FIG. 9;

FIG. 9 shows a side sectional view of the third em bodiment taken along the line IXIX in FIG. 10;

FIG. 10 shows a top sectional view of the third embodiment taken along the line XX in FIG. 9;

FIG. 11 shows a side sectional view of a fourth embodiment. having rotational motion and a double locking arrangement, taken along the line XIXI in FIG. 12;

FIG. 12 shows a part sectional top view of the fourth embodiment along the line XII-XII in FIG. 11;

FFIGS. 13,130 and 14 show a fifth embodiment in which a piston is displaced by an auxiliary ignitor;

FIG. 15 shows a side sectional view of a sixth embodiment, composed of N modules having N-I piston displacements, taken along the line XV-XV in FIG. I6;

FIGS. 16 and 17 show front and top views, respectively, of the embodiment of FIG. I5;

FIG. I8 shows a block diagram of a plurality of the modules of FIGS. 15-17 joined together;

FIG. 19 shows a top part sectional view of a seventh embodiment, having rotation movement, along a line XIX-XIX in FIG. 20; and

FIG. 20 shows a side sectional view of the seventh embodiment along a line XX-XX in FIG. 19.

In the embodiment shown in FIGS. 3-5, a movable drawer l is slidably contained in a guide housing 2 provided with igniters II, Ila. A piston 3 is slidably mounted in the drawer l to define an expansible chamber 16 between one end of the piston and one wall of the drawer. A spring loaded stop 4 is provided in one end wall of the drawer l and is urged by a spring 12 into engagement with an orifice 13 of igniter 11 to lock the drawer with respect to the igniter. A pawl 5 contained in the piston is biased by a spring 14 to engage a groove in the interior wall of the guide 2 to prevent movement of the piston in a reverse direction. A guide rod 7 is connected to the piston through an end wall of the drawer l and has a shoulder 6 which abuts against the end wall to limit forward movement of the piston. An expansion spring 10 normally urges the piston in the forward direction. Gas escape passages 9, 9a communicate interior chambers (such as expansible chamber 16) with the outside atmosphere When the igniter 11 is triggered, the resultant increased gas pressure forces the stop 4 out of its socket in orifice 13 to allow the drawer to be moved in the forward direction (to the left in FIG. 4) due to the pressure of the gas entering the expansible chamber 16 through orifice 17, separated from orifice 13 by a baffle 18. Since the piston 3 is prevented from moving in the reverse direction (to the right in FIG. 4) by the beveled pawl 5, the drawer 1 moves in the forward direction until the stop 4 engages a socket in an orifice 13a in the housing for igniter 11a. As the drawer 1 moves toward igniter 110, it causes expansible chamber 16 to be allowed to communicate with the atmosphere through gas escape passage 90. When the pressure in chamber 16 returns to ambient, spring 10 urges piston 3 in the forward direction to the limit its travel, determined by stop 19 in groove 20 of the drawer, at which time pawl 5 engages the groove 15a in the wall of the guide 2. At this time, the piston 3 will close passage 90 to cut off communication to the atmosphere from chamber 16.

FIGS. 8-10 show a variation of the above described embodiment in which additional igniters 11b, 11c (hav' ing orifices 13b and 17b and 130 and 17c, respectively) are provided along with corresponding additional gap escape passages 9b, 9c, stop 40, pawl 50, and beveled grooves 15b and 150. Orifices l3 and 17 are in open communication with corresponding orifices 13b and 17b, respectively, so that drawer movement can be initiated, in the manner described above, by either one or both of igniters l1 and 11b. The purpose of this arrangement is to further stabilize the device and decrease its sensitivity to vibrations in order that it may operate in severe environments.

FIGS. 13 and 14 show a still further modification in which an auxiliary igniter may be provided in place of the return spring 10 to push the piston 3 in the forward direction by causing gases to expand in the chamber 24 located on the opposite side of the piston from chamber 16. In this embodiment, after the drawer 1 has moved in the forward direction of one cycle, and the piston 3 has been pushed in the same direction by the firing of the igniter 23, chamber 24 is allowed to communicate with the atmosphere through gas escape passage 9 to return that chamber to ambient pressure.

In the above described embodiments, igniter residues might accumulate as a result of their functioning, therefore causing the devices moving parts to foul; this may occur despite any filtering. This drawback limits the number of steps achievable and reduces the systems reliability.

The following embodiment, described with respect to FIGS. 14-18 eliminates this drawback. According to this aspect of the present invention, the pyrotechnically controlled modular, mechanical stepping drive com prises an assembly of N identical modules allowing N-l piston displacements, where the piston is mechanically locked in place at the end of each (drawer) motion and then readied for the next ignition.

Each module comprises:

1. A cylinder aligned with those of the two adjacent modules and within which a motor piston moves;

2. A shuttered combustion head (shutter-breech") performing a double role: (a) locking the motor piston into position the moment it appears in the module, and (b) sealing the cylinder after the pistons passage;

3. A retractable stop maintaining the shutter-breech in the ready or waiting position. This stop is also supported by the module body and is biased towards locking position;

4. A control igniter (except for the last module), the

ignition of which causes the motorpistons unlocking and displacement; and

5. A gas escape hole.

The module 32 shown in FIG. 15 is preceded by a rear plate 37 simulating the previous module and is followed by a front plate 38 simulating the next module.

The device consists of an assembly of N modules 32 within which a motor-piston 31 may move; each mod ule passes through three stages: the initial one, the armed one, and the functioning one.

Each module 32 includes a shutter breech 33 disposed on one end wall of the module and normally urged downwardly by springs 40 to close off cylinder 42 from the entrance to the next succeeding module 38. A stop 34 is pivotally mounted on the axle of the locking piston 35. In the initial state, the stop 34 engages the shutter breech 33 and a niche in the module 32 to hold the shutter breech 33 upwards against the force of the springs 40, thereby maintaining the passageway 42 substantially open. An igniter 36 is disposed in the shell of the module and communicates by way of a passage 44 with the cylinder 42 and by way of a passage 46 with an expansible chamber beneath the lower part 35' of the locking piston 35.

In the initial state, the piston 31 is absent from the module 32; the module 32 shifts to the armed state after the piston 31 has been fired into it from the preceding module 37.

When the piston is tired into module 32 (the Nth stage) from module 37 (the N-l stage) the piston 31 will be locked in place by the shutter-breech 33, while the shutter-breech from the preceding module 37 seals the rear side of the cylinder 42. The module of order N is now armed.

In the functioning stage, the gases caused by igniter combustion cause the locking piston 35, and therefore stop 34, to move upwardly. By this movement, stop 34 pivots at the same time moving shutter breech 33 further upward, thereby releasing the piston 31 which is pushed into the next module 38 by the gases expand ing in the chamber 42 behind the pistonv During piston motion, an escape hole 39 is opened to bring the pressure in the expansion chamber back to ambient and limit the action of the gases. The locking pistons motion is such that the stop 34 pivots by 90 and moves out of the way, thus releasing the piston; after the piston moves into module 38, shutter-breech 33 is forced downward by springs 40 and seals the cylinder, thus readying the ignition of the next module, which thereby is armed.

Centering pins 41 ensure correct alignment of the diverse modules.

The above described embodiments have the common feature that they are all concerned with linear motion of the movable members, either the expansible drawer l or the piston 31. The embodiments shown in FIGS. 6 and 7, l1 and 12, and 19 and 20 are all directed to the rotational movement of the movable members. These embodiments will be described more fully hereinafter.

The basic operating principle behind the rotational motion embodiments is substantially the same as that for the linear motion ones. Therefore, the elements of the rotational mechanisms which correspond to those in the translational structures have been identified with primed reference numerals corresponding to the reference numerals in the translational motion embodiment.

Thus, in FIGS. 6 and 7, a movable drawer 1' is mounted in a circular guide 2' for rotation about a central axis A. The drawer 1' is connected to an axle 12 by a radially extending portion 51. An arcuately shaped piston 3' is contained in arcuately shaped drawer I in substantially the same way as in the linear motion embodiment shown in FIG. 4. The piston 3' is also mounted for rotation about the central axis A, by a radial extension 52 connecting the piston with axle 12, in order to eliminate the need for the guide rod of the linear motion embodiments.

A stop pin 8' is mounted on the radially extending portion 51 of the drawer 1. The return spring 10 is mounted coaxially about the axle 12 and exerts a force to move the piston 3 rotationally (in a counterclockwise direction in FIG. 7).

When the igniter 4 is fired, gases are caused to expand in chamber 16', thereby forcing drawer 1' to move in the forward direction until stop 4' engages the opening 13' in the housing of igniter 11. In one stepped motion, the drawer 1' moves an angular distance L. When the drawer has moved almost the distance L, vent 9a is opened to communication with chamber 16', thereby allowing gases in the chamber to escape and lower its pressure to ambient. The force exerted by return spring 10 is now sufficient to move the piston a corresponding distance L to its new initial position.

The embodiment shown in FIGS. 11 and 12 is a modification of the just described embodiment of FIGS. 6 and 7 and is the rotational equivalent of the linear motion embodiment of FIGS. 8-10 (which is a modification of the first described embodiment of FIGS. 3-5). The operating aspects of this embodiment have essentially all been described above and no further explanation is necessary since the operation of this modification of the embodiment of FIGS. 6 and 7 will be readily apparent from the previous descriptions.

In the rotational embodiments described above, it is possible that residues from igniter combustion may accumulate and foul the moving parts of the device despite filtering. Such an accumulation of residues tends to limit the number of steps and reduces the reliability of the system.

Accordingly, the pyrotechnically controlled rotational motion stepping drive shown in FIGS. 19 and 20 is designed to lessen this problem and comprises a stater 71 housing igniters 78, 78a, etc. disposed radially of the central axis A". The doughnut shaped stater 71 houses a movable rotor member 72 which also rotates about the central axis A" and is connected to a motor shaft 84. The rotor houses a radially extending piston 73 having a stop 73a biased by a spring 74 into engagement with an orifice 85 in the igniter housing. The piston itself is mounted in a radially extending cylinder 96 in the rotor on a radially slidable shaft 86 having a head 87. A lever is mounted in the rotor housing of the stater for both translational and rotational movement. A spring 76 resiliently connects the lever 75 with the stater 72 and urges the lever into engagement with one of a plurality of recesses 88 of the stater through a joint 80, such as a ball and socket joint. Lever 75 is also connected to the rotor 72 by an axle 79 which extends through an elongated opening 89 in the rotor. The long axis of opening 89 extends radially of the central axis A".

A groove 90 is formed in the rotor as a periphe rial extension of the expansible chamber 91; the purpose of the groove 90 is to maintain the chamber 91 in communication with the igniter orifice over percent of the rotational distance travelled by the rotor in one stepped cycle. A gas escape orifice 77 is opened to communication with the expansible chamber 91 by radial movement of the piston 73 to allow the expanding gases in the chamber to escape, thereby returning the chamber 91 to ambient pressure. A further passageway 92 allows the rear chamber of the piston cylinder 96 to communicate with orifice 85 of the igniter 78 after the rotor has essentially completed one stepped movement; this permits residual gases remaining in the orifice 85 to expand into the rear chamber of the piston cylinder to assist the spring 74 to push the piston into locking engagement with the orifice 85a of igniter 78; the residual gases thereafter escape through the conduit 77, which is now open to communicate with this rear chamber.

The operation of this embodiment is described hereinafter. The device is shown in its initial position in FIG. 19, which shows the device in bottom section, with the stop 73a engaged in the orifice 85 of the igniter 78. When this igniter is fired, the expanding gases act on the piston 73 against the normal urging action of the spring 74. Stop 73a thereupon disengages from orifice 8S, permitting the rotor to be rotated about the central axis A". The movement of the piston urges the head 87 ofshaft 86 into contact with lever 75, the force vector of the head extending substantially in a radial direction. The lever is in turn pivoted about the joint 80, at the same time exerting a force on the rotor through the axle 79 to urge it into a rotational movement (clockwise in the plane of FIG. 19). This action is sufficient to move the rotor over approximately 92 percent of the distance between igniters 78 and 78a. When the rotor has moved 92 percent of its total travel distance, the piston has moved a sufficient radial distance so that port 77 is opened to communication with the atmosphere, thereby cutting off the motive force of the piston; the rotor moves the remaining distance by inertia.

At the completion of one rotational step of the rotor 72, spring 86, one end of which has been pivoted along with the lever 75 and the other end rotated with the rotor 72, exerts sufficient force to pull the lever out of one recess 88 into the next succeeding one. At this point, the device has completed one stepped movement and is in the next initial positionready for the above described operation to be repeated.

The above described invention. in all its embodiments. is applicable to any mechanical or electromagnetic system needing to be driven. and the inventions dimensions may be fitted to the power requirement necessary for a given application.

What is claimed is:

l. A mechanical stepping drive apparatus. compris ing:

a housing having a guide chamber formed therein;

first and second pyrotechnic igniters contained in said housing along and in communication with said guide chamber;

a movable member mounted in said guide chamber for step-bystep sliding movement in a forward direction in said guide chamber;

stopping means for substantially preventing sliding movement of said movable member in a reverse di rection;

locking means for locking said movable member into engagement with said first igniter;

unlocking means for unlocking said movable member from engagement with said first igniter by gas pressure produced upon ignition of said first igniter; and

urging means for urging said movable member into sliding movement one step in said forward direction in said guide chamber toward and into locking engagement with said second igniter upon ignition of said first ignitor.

2. A mechanical stepping drive apparatus as defined in claim 1. wherein: said locking means comprises a stop member resiliently mounted in said movable member for engagement with an orifice of said ignitcrs; and said unlocking means comprises a shoulder of said stop member against which expanding gases produced by the operation of said igniters act to push said stop mem her out of engagement with the igniter orifice.

3. A mechanical stepping drive apparatus as defined in claim 1, wherein said movable member comprises a slidable drawer and a piston disposed for sliding movement in said forward direction in said drawer. said piston and drawer defining an expansible chamber; com municating means connecting said first igniter with said expansible chamber for channeling expanding gases produced by the operation of said first igniter into said expansible chamber. wherein the expanding gases in said expansible chamber act on said drawer and piston to urge said drawer in said forward direction.

4. A mechanical stepping drive apparatus as defined in claim 3, wherein said stopping means comprises a beveled stop member resiliently mounted in said piston and one of a plurality of grooves formed in said guide chamber with which said beveled stop member cooper ates to prevent said piston from movement in said reverse direction; and further comprising moving means for moving said piston after said drawer is locked into engagement with said second igniter. said moving means comprising a gase escape conduit communicat ing said expansible chamber with the atmosphere when said drawer is locked in engagement with said second igniter.

5. A mechanical stepping drive apparatus as defined in claim 4, wherein: said moving means further comprises spring means urging said piston in said forward direction at the termination of forward motion of said drawer.

6. A mechanical stepping drive apparatus as defined in claim 4, wherein said moving means comprises an auxiliary igniter and a second expansible chamber defined by said piston and said drawer on the opposite side of said piston from the first mentioned expansible chamber. wherein expanding gases produced by the operation of said auxiliary igniter act on said piston and said drawer to urge said piston into movement in said forward direction.

7. A mechanical stepping drive apparatus as defined in claim 4. further comprising: third and fourth igniters contained in said housing and symmetrically located opposite said first and second igniters. respectively; second locking means for locking said movable member into engagement with said third igniter; and second unlocking means for unlocking said movable member from engagement with said third igniter, the first and second unlocking means unlocking said movable member when either of said first and third igniters is operated.

8. A mechanical stepping device apparatus according to claim 4. further comprising means independently connecting said drawer and piston to an axle member coincident with a central axis forming the center of a circle defined by a longitudinal axis of said guide chamber, wherein the forward movements of said drawer and piston are rotational.

9. A mechanical stepping drive apparatus as defined in claim I, wherein said housing comprises an assembly of N substantially identical modules connected end to end to form a continuous guide chamber therethrough; said movable member comprises a forwardly slidable piston having a groove formed in the forward portion of the cylindrical surface thereof; and said locking means comprises a shutter-breech disposed at the forward end portion of at least one of said modules and means biasing said shutter-breech in a direction normal to the axis of said guide chamber for engagement with said goove of said piston.

10. A mechanical stepping drive apparatus as defined in claim 9, wherein said unlocking means comprises a second piston having a portion engaging said shutterbreech and conduit means connecting said first igniter I with said second piston for channeling expanding gases produced by the operation of said first igniter against said second piston to urge said shutter-breech out of locking engagement with the first mentioned piston; and said urging means comprises an expansible chamber. the movable wall of which comprises the rear face of said first piston and further conduit means connecting said first igniter with said expansible chamber for channeling expanding gases produced by the operation of said first igniter into said expansible chamber. wherein the expanded gases in said expansible chamber act to urge said piston in said forward direction.

I l. A mechanical stepping drive apparatus as defined in claim 10, wherein the shuttenbreech of the module immediately preceding the module in which said first piston is disposed is biased by the biasing means of said immediately preceding module into a position closing the portion of said guide chamber behind said first piston to form a wall of said expansible chamber against which said expanding gases act to urge said piston in said forward direction.

12. A mechanical stepping drive apparatus. comprisfrom engagement with said first igniter; and urging means comprising a radially movable piston mounted in said rotor for urging said rotor into sliding movement in said guide chamber toward and into locking engagement with said second igniter. 13. A mechanical stepping drive apparatus as defined in claim 12, wherein said urging means further comprises a lever pivotal about one end portion thereof in contact with said stator, and means connecting the other end portion of said lever to said rotor to urge said rotor into rotational movement when said piston contacts said lever to urge said lever into pivotable 

1. A mechanical stepping drive apparatus, comprising: a housing having a guide chamber formed therein; first and second pyrotechnic igniters contained in said housing along and in communication with said guide chamber; a movable member mounted in said guide chamber for step-by-step sliding movement in a forward direction in said guide chamber; stopping means for substantially preventing sliding movement of said movable member in a reverse direction; locking means for locking said movable member into engagement with said first igniter; unlocking means for unlocking said movable member from engagement with said first igniter by gas pressure produced upon ignition of said first igniter; and urging means for urging said movable member into sliding movement one step in said forward direction in said guide chamber toward and into locking engagement with said second igniter upon ignition of said first ignitor.
 2. A mechanical stepping drive apparatus as defined in claim 1, wherein: said locking means comprises a stop member resiliently mounted in said movable member for engagement with an orifice of said igniters; and said unlocking means comprises a shoulder of said stop member against which expanding gases produced by the operation of said igniters act to push said stop member out of engagement with the igniter orifice.
 3. A mechanical stepping drive apparatus as defined in claim 1, wherein said movable member comprises a slidable drawer and a piston disposed for sliding movement in said forward direction in said drawer, said piston and drawer defining an expansible chamber; communicating means connecting said first igniter with said expansible chamber for channeling expanding gases produced by the operation of said first igniter into said expansible chamber, wherein the expanding gases in said expansible chamber act on said drawer and piston to urge said drawer in said forward direction.
 4. A mechanical stepping drive apparatus as defined in claim 3, wherein said stopping means comprises a beveled stop member resiliently mounted in said piston and one of a plurality of grooves formed in said guide chamber with which said beveled stop member cooperates to prevent said piston from movement in said reverse direction; and further comprising moving means for moving said piston after said drawer is locked into engagement with said second igniter, said moving means comprising a gase escape conduit communicating said expansible chamber with the atmosphere when said drawer is locked in engagement with said second igniter.
 5. A mechanical stepping drive apparatus as defined in claim 4, wherein: said moving means further comprises spring means urging said piston in said forward direction at the termination of forward motion of said drawer.
 6. A mechanical stepping drive apparatus as defined in claim 4, wherein said moving means comprises an auxiliary igniter and a second expansible chamber defined by said piston and said drawer on the opposite side of said piston from the first mentioned expansible chamber, wherein expanding gases produced by the operation of said auxiliary igniter act on said piston and said drawer to urge said piston into movement in said forward direction.
 7. A mechanical stepping drive apparatus as defined in claim 4, further comprising: third and fourth igniters contained in said housing and symmetrically located opposite said first and second igniters, respectively; second locking means for locking said movable member into engagement with said third igniter; and second unlocking means for unlocking said movable member from engagement with said third igniter, the first and second unlocking means unlocking said movable member when either of said first and third igniters is operated.
 8. A mechanical stepping device apparatus according to claim 4, further comprising means independently connecting said drawer and piston to an axle member coincident with a central axis forming the center of a circle defined by a longitudinal axis of said guide chamber, wherein the forward movements of said drawer and piston are rotational.
 9. A mechanical stepping drive apparatus as defined in claim 1, wherein said housing comprises an assembly of N substantially identical modules connected end to end to form a continuous guide chamber therethrough; said movable member comprises a forwardly slidable piston having a groove formed in the forward portion of the cylindrical surface thereof; and said locking means comprises a shutter-breech disposed at the forward end portion of at least one of said modules and means biasing said shutter-breech in a direction normal to the axis of said guide chamber for engagement with said goove of said piston.
 10. A mechanical stepping drive apparatus as defined in claim 9, wherein said unlocking means comprises a second piston having a portion engaging said shutter-breech and conduit means connecting said first igniter with said second piston for channeling expanding gases produced by the operation of said first igniter against said second piston to urge said shutter-breech out of locking engagement with the first mentioned piston; and said urging means comprises an expansible chamber, the movable wall of which comprises the rear face of said first piston and further conduit means connecting said first igniter with said expansible chamber for channeling expanding gases produced by the operation of said first igniter into said expansible chamber, wherein the expanded gases in said expansible chamber act to urge said piston in said forward direction.
 11. A mechanical stepping drive apparatus as defined in claim 10, wherein the shutter-breech of the module immediately preceding the module in which said first piston is disposed is biased by the biasing means of said immediately preceding module into a position closing the portion of said guide chamber behind said first piston to form a wall of said expansible chamber against which said expanding gases act to urge said piston in sAid forward direction.
 12. A mechanical stepping drive apparatus, comprising: a housing comprising a guide chamber and a cylindrical stator surrounding said guide chamber; first and second pyrotechnic igniters disposed circumferentially in said stator in communication with said guide chamber; a movable member comprising a rotor mounted for rotational movement coaxially with the central axis of said stator and disposed for sliding movement in a forward direction in said guide chamber; stopping means for stopping said movable member from sliding movement in a reverse direction; locking means for locking said movable member into engagement with said first igniter; unlocking means for unlocking said movable member from engagement with said first igniter; and urging means comprising a radially movable piston mounted in said rotor for urging said rotor into sliding movement in said guide chamber toward and into locking engagement with said second igniter.
 13. A mechanical stepping drive apparatus as defined in claim 12, wherein said urging means further comprises a lever pivotal about one end portion thereof in contact with said stator, and means connecting the other end portion of said lever to said rotor to urge said rotor into rotational movement when said piston contacts said lever to urge said lever into pivotable movement. 